Flashing lights have often been used to indicate danger or emergency to persons approaching the light. These lights are usually operated by a power source such as a battery, internal combustion engine, normal electrical source, etc. Even though these power sources are complex and expensive, they have been required to operate a glowing bulb such as an electric light in combination with some type of electrical flashing device. In spite of their complexity and expense, these devices deteriorate and cannot be depended upon for use in an emergency.
With particular reference to motor vehicles, flares have been used to indicate a disabled vehicle or some other emergency situation. These flares are usually placed some distance away from the place where the vehicle is stopped. Depending on the terrain, often the flares will be out of view of the operator who has placed them. Consequently, when the flares have burned out the operator will not be aware of that fact putting him in a perilous position as oncoming cars will not be warned of the approaching situation.
Similar problems arise with battery operated flashing devices. Often they are stored for long periods of time before being used resulting in deterioration of the battery. When the device is finally used it may not work properly, if at all.